Organocatalytic Hydrogen Evolution Reaction by Diazaphospholenes

The electrochemical hydrogen evolution reaction (HER) is currently recognized as a prospective way to obtain clean energy. The electrocatalysts used currently are dominantly based on transition metals. In this work, we have demonstrated a diazaphospholene (N-heterocyclic phosphine (NHP))-type small molecular organocatalyst that can catalyze the HER with a maximum current density of 130 mA·cm^-2, an overpotential of 354 mV, and a faradaic efficiency of 90%. Mechanistic studies verify a Heyrovsky-type process with NHP, whereas its hydricity and aromaticity favor hydrogen release and catalyst regeneration.